Transformer voltage regulator



Dec. 8, 1936. O C TY 2,063,693

TRANSFORMER VOLTAGE REGULATOR Filed June 20, 1936 ay/mi Inventor: Orin P. Mo Carty,

b /wyMMAM Hls Attorney.

Patented Dec. 8, 1936 Orin P. McCarty, Pittsfield,

Mass, assignor to General Electric Company, a corporationof New York 1 Application June 20, 1936, Serial No. 86,413

My invention relates to transformer voltage rupting the load current and with the produc- I tion of minimum voltage disturbance in. the

transformer circuit. Heretofore I have Qdone this by changing taps on the secondary or series winding of the transformer and during the tap changing operation I have caused the transformer load current to flow through a nonlinear characteristic current by-pass.

In accordance with my present invention I provide a novel and simple transformer voltage regulating circuit in which the connections in the main load current carrying circuit are not changed during a regulating step 'and the change in voltage is secured by'cha ing the connections of the transformer exciting winding and I provide-a non-linear characteristic impedance for limiting the voltage across the excit-' ing winding and hence, limiting the voltage drop across the secondary or series winding of the transformer during, a voltage or ratio changing operation. An object of my invention is to provide a' new and improved voltage regulating transformer.

, Another object of my invention is to provide a new and improved automatic transformer voltage regulator. v Another object of my invention is to provide a newand improved way of changing the ratio of a transformer under load.

My .invention will be better understood from the following description taken in connection with the accompanying. drawing and its. scope will be-pointed'. out in the appended claims.

In the drawing Fig. l is a simplified diagrammatic showing of one form of my transformer voltage varying circuit; Fig. 2 is a diagrammatic showing of an automatic transformer voltage regulator embodying my invention and which is adapted for operation on a three-wire alternating current secondary distribution circuit; and Figs. 3 to 10 inclusive illustrate various modified connections between the ratio changing switch or contactor andthe transformer exciting windings for securing various different;'

combinations of maximum voltage. 1 7

Referring now to the drawing and more parand minimum tion the exciting winding 5 is connected across 8' Claims. (01. 171-119) ticularly to Fig. 1, I have shown therein a simple two-wire alternating current circuit I having a source end 2 and a load end 3. Con nected in the circuit l is a regulating transformer having a series winding 4 and a shunt or 5 exciting winding 5, both wound on the same core which is represented by the dotted line 6.

For controlling the connections of the exciting winding -5 there is provided a single-pole, double-throw switch I and for' limiting the im-. pedance of the transformer during a positional change of the switch I a negative impedancecurrent characteristic impedance 8 is connected across the exciting winding 5.

The impedance 8 is preferably one or more pieces of the ceramic resistance material known as 'Ihyrite, the composition of which is disclosed and claimed in Patent 1,822,742, granted September 8, 1931 on an application of K. B. McEachron and assigned to the assignee of they present application. 'This resistance material has the property of reducing its resistance in- -stantaneously and to a very marked extent with constant and independent of the current.

The switch I is so arranged that in one posithe circuit I while in the other position the winding 5 is short circuited.

In the operation of Fig. 1, when the circuit l is connected to a source (not shown) and the switch 1 is in .the position shown,- a predetermined amount of voltage boost or buck, depending upon the relative direction of the current in the windings 4 and 5, will be produced by the series winding 4 in the main circuit. The impedance 8 is so 40 proportioned that for the normal circuit voltage its impedance or resistance is practically infinite so that substantially all of the current in the shunt circuit flows through the shunt winding 5 and substantially none of the current flows through the impedance 8. If now the switch 1 is moved to the other position the transformer will saturate, if circuit l is carrying load current, as the movable contact of the switch is. passing from one position to the other. The effect of this saturation is to limit to a certain extent the re- "-actance and voltage drop of the winding 4. While switch I is passing between its two contact making positions the series winding 4 will be acting as a primary winding and will tend to induce a relatively very high voltage in the exciting winding 5. For example, if the transformer produces a 10% boost, the voltage tending to be induced in the exciting winding 5 during the operation of the switch will be ten times the circuit voltage. However, before the voltage can reach anywhere near this high value the resistance of the device 8 will decrease so much that the voltage across the exciting winding will be limited to a relatively low value which is not much higher than normal circuit voltage. The importance of this is that it causes the impedance of the regulating transformer, referred to the secondary winding 4, to be not much greater than its impedance when the exciting winding 5 is connected across the circuit. Consequently the voltage drop across the winding 4 during the operation of the switch 1 will be relatively low and will cause hardly any voltage disturbance in the circuit and will not cause lamp flicker if incandescent lamps are energized from the load end 3 of the circuit i. As soon as the switch 1 engages the lower fixed contact the exciting winding 5 and impedance 8 will be short circuited. As the impedance of the short circuit of the winding 5 is substantially zero the impedance of the transformer as a whole will be substantially zero and no voltage buck or boost will be produced in the circuit I.

If the switch I is moved back again to the upper contact the saturation of the transformer due to the load current combined with the voltage limiting effect of the impedance 8 will be the same as before until the positional change has been completed when the exciting winding will be connected across' the circuit and a definite voltage boost or buck will be produced in the circuit i.

In tests on an arrangement as shown in Fig. 1 in which the load voltage was 220 volts and the transformer produced a 10% voltage boost of 22 volts and the load current was 33 amperes, the current switched by the switch 1 was 3.3 amperes and the switch made 350,000 operations with practically no wear on the contacts.

From the above description of Fig. 1 it will be seen that no switching operation takes place in the main load current carrying circuit and that the switching current during the regulating operation is very much less than the main load current so that the switch may be made smaller and less expensive than a switch capable of carrying the main load current. Furthermore, the negative impedance-current characteristic imp edance 8 may be made of small size and consequently at low cost in comparison with an ordinary load current by-pass impedance of this type which is capable of carrying the entire circuit load current.

The complete automatic voltage regulator shown in Fig. 2 is made for operation in a threewire alternating current secondary distribution circuit. This circuit has outer conductors A and B and a neutral conductor N. The usual voltage of such circuits is 230 volts between the outer conductors and volts between each outer conductor and the neutral, as is indicated at the lefthand or source end of the circuit. The regulating transformer is provided with two series windings 4 and 4 connected respectively in the outer conductors A and B. This transformer is also provided with two separate exciting windings 5 and 9. The winding 5 corresponds to the same critical voltage the The switch 1 is arranged to be operated electromagnetically by means of the winding Hi. It is arranged to provide double breaks in the circuit in both directions of operation and has no flexible connection to the moving parts. As shown, it has a movable bridging contact member which in the illustrated position is connecting two contacts II and i2 and in the other position will bridge two contacts i 3 and I4. Essentially, however, it is a single-pole, double-throw switch.

The terminals of the winding 9 are connected respectively to the contacts H and i2 so that the winding 9 is short circulted when the switch 1 is in the position shown. This position will be referred to as the minimum position of the switch. The contacts I2 and I are interconnected by a jumper and contacts l3 and H are connected respectively to the line conductors A and B. With this arrangement, when the coil I0 is energized the switch moves over to position and as the bridging member engages contacts l3 and I 4 the winding 9 will be connected between the line conductors A and B. Consequently, the exciting winding 9 will be energized in such a manner as to induce a regulating volt age boost in the secondary or series windings 4 and 4'.

Switch 1 is controlled automatically in response to voltage by means of a known type of resonant relay i5 comprising an adjustable resistance I6, an adjustable inductance I! and a capacitor II connected in series between the conductor A-and the neutral conductor N. An auxiliary relay I9 is connected across the capacitor l8 and the contacts of this relay control the energization of the operating winding iii of the switch 1.

- The reactor I1 has a magnetically'saturable core and the resonant relay circuit is so arranged that at a predetermined critical voltage the magnetic saturation of the core of reactor l1 causes the inductance of the reactor to neutralize the capacitance of the capacitor l8 throughout a portion of each cycle of the applied voltage thereby producing a condition of partial resonance in the series circuit. At a lower voltage than the circuit is dissonant. At resonance the current through the resonant circuit increases thereby increasing the voltage across the capacitor I 8 and causing the auxiliary relay l9 to open its contacts.

The adjustments on the resistor I 6 and the up and the value at which it drops out, and also for adjusting the relay IS.

The parts are shown in Fig. 2 in the position they will occupy when the system is deenergized. When voltage is applied at the source end of the circuit, the winding III will be energized through the closed contacts of the relay I9 and the switch 1 will be bridging the contacts l3 and I 4 thereby energizing the shunt winding 9 and causing a predetermined voltage boost in the circuit. If the circuit voltage increases to the critical value relay I 9 will pick up thereby deenergizing the winding l0 and causing the switch 1 to snap over to its minimum position in which the contacts i I and I2 are bridged thereby to short circuit the winding 9.

While the switch 1 regulating transformer saturates as in Fig. 1 and the voltage and the impedance of the transformer its other or maximum is changing positions the are limited by the negative characteristic of the impedance 8 because as the winding 5' is on the same core as the other windings it isinductively coupled to all of them. As soon as the switch I reaches its minimum position and the winding 9 is short circuited the impedance of the transformer with respect to the main circuit is substantially zero, so that the regulator may be said to be in its neutral position as it is neither bucking nor boosting. If now the voltage'talls below the critical value the. resonant circuit becomes dissonant, relay l 9 closes thereby energizing winding H) causing the switch 1 to move over to its maximum position and energize the winding 9 so as to cause a desired voltage boost in the main circuit.

e The regulator of Fig. 2 can easily be adapted for use with two-wire instead of three-wire circuits by merely making an interconnection between the conductors B and N. In this case the voltage'applied to the exciting winding or windings of the transformer will be half that with the three-wire circuit and consequently the regulating voltages will be half of what they would be for three-wire operation.

If the ratio of the number of turns of the exciting windings 9 and 5 is 3 to 2 it is possible by ing'5 and the winding 9 will cause the winding 5 to produce a nine-volt raise if the connections correspond to those in the drawing but it they are reversed they will produce a nine-volt lower. In-

cidentally, this connection corresponds tothat shown in Fig. 1 in that the winding 5 is alter-.

nately short circ'uited and excited across the main circuit. If now the windings 5 and 9 are connected diiferentially in series the number of effective turns will be half the number of turns in the winding 5. Consequently, with this diflerential connection it is possible to secure either an l8-volt raise or an 18-volt lower. If now the windings are connected in series cumulatively instead of difierentially the number of eifective turns will be five times that of the diflferential connection so that-the voltage will be V5 of the voltage of the diiferential connection. That is to say, it will be 3.6 volts either raise or lower,

depending upon the polarity of the connections to the series cumulative connection.

In the following table are listed all the various combinations of the above connections so as to give .in all 36 different ranges of regulation. Each of the first eight of the listed connections are illustrated in one of the detailed Figures 3' to 10, inclusive, and in the "table each figure in the drawing, including Figs. Land 2, corresponding to each range of regulation is tabulated. The

voltage V will be 18 volts if the windings 5 and 9 are the same as in Fig. 2 but this need not necessarily be true. However, the table is based on a ratio of turns in the windings 9 and 5, of 3 to 2. Other ratios may be employed if desired. The table and Figures 3 to 10 are arranged in descending order of magnitude of the maximum voltage coupled with a descending order of magnitude of? the minimum'voltage.

Range of regulation Maximum Minimum Figs.

Volts Connections Volts Connections 3 +V Winding 9 booSt- +$V Winding5boosting ing in series with :vinding 5 buckng. 4- +V .do +%V Winding9boosting. 5 +V do +55V Winding 5 boosting in series with wdg. 9boosting. 6 +V do Wdgs. 9 and shorted in series. 7 +V .do -$V Wdg. 9 bucking in series with wdg. 5 bucking.

3 +V .do -%V Windingilhucking. 9 +V .d0 }V Wiuding5bucking. 10 l-V do ,V Wdg. 5 boosting in series with wdg. 9 bucking. +%V Wiinding 5 hoost- +l-$V Windingiiboosting.

ng. +lV do +lV Wdg 5 boosting in series with wdg. 9

boosting. 1 +l-V do 0 Windingfishorted.

+$V do V Wdg. 5 bucking in series with wdg. 9 bucking.

}V Winding 9 bucking. %V Winding 5 bucking.

V Wdg. 5 boosting in series with w g. 9 I bucking. +$V Winding 9 boost- +%V Wdgs. 5 and 9 in ing. series boosting. 2 +%V .do 0 WindingQshorted.

+%V .do %V Wdgs. 5 and 9 in series both buckmg. Winding 9 bucking.

shorted in series.

Wdg. 5 boosting in series with wdg. 9 bioosting 0 shorted in series.

Windingilbucklng. Winding 5 bucking.

Wdg. 9 bucking in series with wdg. 5

n Wdgs. s and 9 -rsv Wdgs. 5 and 9 in shortedinseries. series both bucking. 0 Winding9shorted -%V Windingilbucking. 0 Winding fishorted ',-V WindingBbucking. 0 Wdgs. 5 and 9 V 'Wdg. 9 hucki in series with w g. 5

boosting. %V Wdg.5bucking in %V Winding9bucking.

series with wdg. 9buckin WindlngSbucking.

Wdg. 9 bucking in V series with w g. 5 v w ding9b In I av w i gi 'b n 34 in uc ng :1 ng uc 'ng. -%V .....dc V Wdg. 5 boosting in series with wdg.-9

bucking. -%V Winding 5bucking, V Do.

In Figs. 3 to 10, inclusive, only the switch and the exciting windings 5 and 9 are shown and it is to be understood that these figures merely represent the changes in Fig. 2 necessary to give the various ranges of regulation specified in the table.

It will be noted that in Figs. 3, 5, 7, 8, and 10 it is necessary to employ a double-pole, doublethrow switch instead of the single-pole, doublethrow switch shown in the other figures. This, however, can readily be done in Fig. 2 by merely adding another movable lever, and two other sets of contacts bridged thereby, to be operated by the coil no:

other. This produces substantially the same et- 1 feet as though one winding were short circuited.

While I have shown and-described particular embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications may be made therein and therefore I aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an alternating current circuit, a transformer havinga plurality oi windings including a series winding in said alternating current circuit and an exciting winding, a negative impedance current characteristic impedance connected across one of the windings of said transformer other than said series winding, and a circuit controller for selectively connecting said exciting winding across said alternating current circuit and disconnecting it therefrom.

2. In combination, an alternating current circuit, a transformer having a series winding connected in said alternating current circuit and having an exciting winding, a negative imped ance-current characteristic impedance connected across said exciting winding, and a circuit controller for selectively connecting said exciting winding across said alternating current circuit and short circuiting said winding.

3. In combination, an alternating current circuit, a transformer having a plurality of windings including a series winding in said alternating current circuit and a plurality of exciting windings, a negative impedance-current characteristic impedance connected across one of said exciting windings, and a circuit controller for selectively connecting one of said exciting-windings across said alternating current circuit and short circuiting one of said exciting windings.

4. In combination, an alternating current circuit, a transformer having a plurality of windings including a series winding in said alternating current circuit and a plurality of exciting windings, a negative impedance-current characteristic impedance connected across one of said exciting windings, and a circuit controller for selectively connecting said exciting windings in series relation across said alternating current circuit and for changing. the connections of said exciting windings relative to said alternating current circuit.

5. In combination, an alternating current circuit, a transformer having a series winding in said circuit and having two exciting windings with diiferent numbers of turns, a negative impedance-current characteristic impedance connected across one of said exciting windings, and a two-position switch connected so that in one position one of said exciting windings is connected across said circuit and in the other position said exciting winding is connected in another circuit.

6. In combination, an alternating current circuit, a transformer having a series winding in said circuit and having two exciting windings with difierent numbers of turns, a negative impedance-current characteristic impedance connected across one of said exciting windings, and a two-position switch connected so that in one position one of said exciting windings is connected across said circuit and in the other position the other one of said exciting windings is short circuited.

7. In combination, a single phase, three-wire alternating current circuit, a regulating transformer having series windings connected respectively in the two outer conductors of said circuit and having an exciting winding, and a switch for selectively connecting said exciting winding across said circuit and disconnecting it therefrom.

8. In combination, a main alternating current circuit, a transformer having a series winding in said circuit and an exciting windingadapted to be connected across said circuit, a negative impedance-current characteristic impedance connected across said exciting winding, a switch for selectively connecting said exciting winding across'said circuit and connecting it in another circuit, and means responsive to the voltage of said main circuit for controlling the operation of said switch.

ORIN P. McCARTY. 

